Tamper detection and prevention for an object control and tracking system

ABSTRACT

Tamper detection and prevention for an object control and tracking system and particularly a Key Track system is provided. Where objects being tracked are keys, a key card having a touch memory device, RF id tag, or other circuitry for storing and transmitting an ID to a controller is provided. A tether attaches a key to the card. In one embodiment, the tether is conductive and the transmission of the ID code passes through the tether. If the tether is cut, transmission is interrupted to indicate a tampering condition. In another embodiment, the tether is resistive and circuitry is provided to monitor a voltage drop across the tether. A change in the voltage drop indicates a tampering condition. An object of the invention is to detect an attempt to remove the key (or other object) from its ID card while leaving the card intact.

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of the filing date of priorfiled U.S. Provisional patent application Ser. No. 60/099,954, filedSep. 11, 1998.

TECHNICAL FIELD

[0002] This invention relates generally to object tracking and controlsystems and more particularly to systems for tracking and controllingaccess to and disposition of objects such as keys and to enhancementsusable with such systems to detect and prevent tampering with orattempts to defeat the systems.

BACKGROUND

[0003] Many objects have intrinsic value or have value because theyprovide access to other valuable objects. For instance, jewelry andcoins have inherent intrinsic value while keys, such as keys tovehicles, have value because they provide access to other valuableobjects, namely automobiles and trucks. Further, access to and controlof some items, such as narcotics for example, needs to be monitored,tracked, and controlled to assure against unauthorized access or assurethat proper and appropriate accesses is catalogued. There is a seriousneed to be able to track, catalogue access to, and control such objectsin a way that is reliable, simple to implement, and virtually tamperproof.

[0004] In the past, a variety of systems have been implemented to trackand control objects. In the case of keys in an automobile dealership,for example, pegboards have been used to keep track of the keys as salespersons, maintenance personnel, and others remove keys for access tovehicles. Generally, sign out sheets are used to log the check-in andcheckout of such keys. Obviously, such a manual system of tracking hasnumerous shortcomings due in large part to the very real potential ofhuman error and forgetfulness in carrying out the sign-in and sign-outprocedures.

[0005] More recently, automated computer controlled key tracking systemshave been implemented for tracking, for example, vehicle keys at carlots and keys to the apartment s of apartment complexes. One such systemparticularly applicable to the present invention is the key trackingsystem disclosed and claimed in my U.S. Pat. No. 5,801,628, thedisclosure of which is hereby incorporated fully by reference. In thedisclosed system, referred to herein as the “Key Track” system, keys toa vehicle are attached with a rivet, tether, or the like to a thinplastic key tag or card having a depending tongue. The tongue carries asmall button shaped electronic touch memory device, which electronicallystores an ID code. The tongue of each key card is configured to beinsertable in any of an array of slots formed in a top panel within astorage drawer. A printed circuit backplane is disposed beneath the toppanel and is provided with a plurality of pairs of metal contacts, eachpair of contacts being aligned with a corresponding one of the slots inthe top panel. When the tongue of a key card is inserted in a selectedone of the slots, its touch memory device is engaged by thecorresponding pair of contacts.

[0006] A computer or microprocessor or microcontroller based controlleris electronically coupled through a communications matrix to thecontacts on the backplane and periodically polls each pair of contacts,preferably several times per second, to determine the presence orabsence of a touch memory device and thus which slots contain key cardsand which do not. More specifically, if no information is received froma particular pair of contacts when polled, it is determined that theslot corresponding to the pair of contacts is empty. When a slotcontains a key card, the touch memory device of the card responds to thepoll by transmitting its ID code, from which the identity of theparticular key attached to the card can be determined through a tablelookup. In this way, the absence or presence and location in the storagedrawer of key cards and their associated keys can be noted by thecontroller each time the array of contacts are polled. If a card presentin a slot on a prior polling is absent on a subsequent polling, then thecontroller notes that the card and its key have been removed from thestorage drawer. Conversely, if a key card is detected in a previouslyempty slot, the controller notes that the card and its key have beenreplaced in the storage drawer. The removal and replacement of keys istherefore continuously monitored.

[0007] An access feature requires an authorized user such as a salesperson to enter an ID code to unlock and access the storage drawer. Whenthe history of removal and replacement of key cards and their keys iscombined with other information, such as the time at which cards areremoved and replaced and the identities of the persons who accessed thedrawer and times of access, access to the keys in the drawer can becontrolled and a detailed tracking log can be created. This Key Tracksystem greatly decreases instances of lost keys, reduces the timerequired to find checked-out keys, and generally provides automatictracking and control of the keys, and thus, to a large extent, controlsand tracks the vehicles to which the keys provide access.

[0008] As an alternative to a Key Track system using touch memorydevices requiring physical engagement with conducting contacts,non-contact transmission of ID codes to the controller are alsopossible. Such systems make use of radio frequency (RF) tags on the keycards with the tags having an integrated circuit chip storing the IDcode and perhaps other information and an antenna attached to the chip.The antenna can be a capacitive plate antenna, an inductive loopantenna, a dipole antenna, or another type of antenna. The backplane ofthe system includes an array of sensors in the form of antennas that arepositioned to align with the antennae on the key cards when the cardsare inserted within their slots or receptacles in the storage unit.Information is transmitted from the cards to the controller via radiofrequency transmission or modulation from the antennas on the key cardsto the sensor antennas on the backplane. Aside from the non-contactmethod of data transmission, the functionality of such systems is muchthe same as a system using touch memory devices.

[0009] While the Key Track system described above has proven extremelyvaluable in the tracking and control of keys, it nevertheless hascertain problems and shortcomings inherent in its design. One suchproblem is the potential for tampering and system defeat simply bycutting the key card or cutting the key in order to remove the key fromthe card without removing the card from the Key Track storage drawer. Insuch an event, the key card remains in its slot so the Key Trackcontroller fails to note any suspicious activity, thinking instead thatthe key is still secure within the storage drawer. Even though asubsequent user of the system my notice that the key has been removedfrom its card, this may not occur for some time and, by then, the key(or other valuable object that may have been attached to the card) maywell be beyond recovery. Further, relying on humans to report systemcompromises allows for the potential for conspiracy, and is thusgenerally not reliable.

[0010] Thus, a need exists for a method and system for detectingtampering and attempted defeat of a Key Track system by removing a keyor other valuable item from its Key Track card while leaving the cardintact within the Key Track storage drawer. In a broader sense, thesystem should be adaptable for use with Key Track systems utilizingtouch memory devices and non-contact RF tag devices for storing andtransmitting ID codes to the system controller. The system should bereliable, should indicate tampering with a high level of confidence whenit occurs, and should operate autonomously without the need for relyingon human intervention for detecting and reporting tampering. It is tothe provision of such a method and system that the present invention isprimarily directed.

SUMMARY OF THE INVENTION

[0011] Briefly described, the present invention, in one preferredembodiment thereof, comprises a method and apparatus for detectingtampering with a Key Track system through attempted removal of a trackedobject from its ID card. In the preferred embodiment, the object is akey, but may also be other types of objects trackable with a Key Tracksystem as detailed below. In its broadest sense, the apparatus comprisesa tether made of a conducting or resistive material and attaching thekey to its key card. The tether forms a conducting or resistive loopthrough which a current can flow when the tether is intact. In oneembodiment, the touch memory device or RF tag communicates to the systemcontroller directly through the tether loop. In another, the currentflowing through the tether and consequent voltage drop across the tetheris monitored by a microcontroller fixed to the ID card.

[0012] In the case of a tether loop through which the ID devicecommunicates directly, if the tether loop is cut to remove the key, orof the card is cut, the ID device ceases to communicate with thecontroller. The controller logs this as the key card having been removedfrom the system. Since the user who tampered with the system entered hisor her authorization code to access the drawer, the perpetrator will beisolated and identified at a later time when the missing key is noticed.Thus, tampering is detectable and, consequently, deterred by the system.

[0013] In an alternate and more robust embodiment of the invention, thetether contains a resistive core and a microcontroller on the key cardconstantly monitors a voltage drop across the tether. If the resistancechanges because the tether is cut, shunted, or damaged, themicrocontroller notes the event and can report a suspicious conditionimmediately to the central controller. The controller can then issueappropriate alarms and alert security personnel. This embodiment is animprovement over the simple conducting tether because it eliminates thedelay between the tampering and its detection and also eliminates theneed for a human to notice the missing key.

[0014] The invention also includes stainless or hardened key shrouds forpreventing a would be thief from cutting a key directly to remove itfrom its tether while leaving the tether intact. A furtherimplementation of the invention comprises a bag for containing an objectto be tracked. The bag is formed with a conductive or resistive mesh,preferably embedded within the material of the bag. The mesh is definedby a strand of material that is formed into the crisscrossing pattern ofthe mesh and has two ends. The bag is closed and sealed by a hingedseal, which carries a touch memory or other ID device and that hascontacts that engage the two ends of the mesh strand. The seal isinsertable in a receptacle of a Key Track system in the usual way. Ifthe bag is cut, the continuity of the mesh is destroyed and this eventis detected and conveyed to the central controller for alarm generation.Thus, the object in the bag is secured against being cut from the bagand taken from the Key Track system. Other variations of the inventionare also envisioned, as described in more detail below.

[0015] Thus, an apparatus and method is now provided that successfullyaddresses a vulnerability of the basic Key Track system by effectivelyand reliably detecting and preventing attempts to defeat the system bycutting a key or other object from its key card. In some embodiments,the invention is readily usable with the basic existing Key Tracksystem. In other embodiments, tampering is detected immediately andappropriate alarms are sounded. These and other features, objects, andadvantages of the invention will become apparent upon review of thedetailed description set forth below when taken in conjunction with theaccompanying drawings, which are briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a perspective partially exploded view of an apparatusfor tamper detection and prevention in a Key Track system that embodiesprinciples of the invention in a preferred form.

[0017]FIG. 2 is a perspective partially exploded view of an alternateembodiment of a tamper detection and prevention apparatus for a KeyTrack system.

[0018]FIG. 3 is a perspective partially exploded view of yet anotherembodiment of an apparatus for tamper detection and prevention in a KeyTrack system.

[0019]FIG. 4 is a perspective view illustrating attachment of a keytether and key to the embodiment of FIG. 3.

[0020]FIG. 5 is a perspective view illustrating yet another embodimentof the apparatus of this invention for detecting tampering with atracked object stored in a bag.

[0021]FIG. 6 is a perspective view of a resistive tether for use withthe tamper detection and prevention apparatus of this invention.

[0022]FIG. 7 is an electronic schematic diagram of a simple circuit foruse with the embodiment of FIG. 6.

[0023]FIG. 8 is a perspective partially exploded illustration of atamper detection and prevention apparatus that embodies principles ofthe invention in still another form.

[0024]FIG. 9 is an electronic schematic diagram of a circuit usable torealize the embodiment of FIG. 8.

[0025]FIGS. 10 and 11 are perspective views illustrating a stainless orhardened steel shroud for prevent a key from being cut from its tetherin a Key Track system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Referring now in more detail to the drawings, in which likenumerals refer to like parts throughout the several views, FIG. 1illustrates a key tag assembly that embodies principles of the inventionin a preferred form and that is adapted for use with an existing KeyTrack system. The key tag assembly 11 comprises a key card 12 formedwith a main body 14 and a depending tongue 16. The key card is encasedin a sheath or protective casing 13 to enclose and protect internalcomponents of the assembly. The key card 12 can be made of a variety ofmaterials such as, for example, printed circuit board material, plasticswith or without embedded components, or other appropriate material.

[0027] A touch memory device 17 is mounted to the tongue 16 of the keycard and is securely held on one side thereof by a retainer 18. Unlikethe traditional Key Track system, the touch memory device is not mountedthrough a hole in the tongue and therefore the device is exposed only onone side of the tongue rather that being exposed on both sides. A firsttether retaining tube 19 made of electrically conducting material issecured to the key card extending along the length thereof and a secondtether retaining tube 21 also made of electrically conducting materialis secured to the card spaced from and generally parallel to the firsttube 19. The first tether retaining tube has an open top end 20 and aclosed bottom end (not visible) and the second tether retaining tube hasan open top end 22 and a closed bottom end (not visible). The bottomends of the tether retaining tubes may also be open if desired and theopen top ends of the tubes are exposed on the top of the tag assembly.Further, instead of being formed of an electrically conducting material,the tubes 19 and 21 may be made of insulating material or maybe providedwith an internal or external conductor extending therealong.

[0028] A conductive contact pad 26 is formed on the side of thedepending tongue opposite the side on which the touch memory device ismounted and preferably is formed by printed circuit etching techniques.A printed circuit trace 24 electrically connects the contact pad 26 tothe first tether retaining tube 19. A printed circuit board trace 23electrically connects the second tether retaining tube to one of thecontact surfaces of the touch memory device, which is the contactsurface that normally is exposed on the back side of the dependingtongue 16 in a traditional Key Track key card. The other contact surfaceof the touch memory device is exposed just as it is in the traditionaltag.

[0029] An electrically conducting tether 27 has a first locking end 28and a second locking end 29 connected by a tether loop 31. The lockingends 28 and 29 preferably are spring biased as illustrated so that theycan be pressed together but, when released, spring back out to theirexpanded configurations. The open ends 20 and 22 of the tether retainingtubes are formed with interior lips or rims that form catches for thelocking ends of the tether. With this configuration, the locking ends ofthe tether may be inserted into the open ends of the tether retainingtubes, where they snap securely into place to lock the ends of thetether in the ends of the tether retaining tubes. When the tether loop31 is extended through the opening 33 of a key 32 prior to its endsbeing pressed into the tether retaining tubes, it will be seen that thekey is securely tethered to the assembly. Further, since the tether isconducting, locking of the tether in the tether retaining tubes forms aclosed electric circuit between the contact pad 26 on the back of thedepending tongue 16 and the corresponding contact surface of the touchmemory device 17. Obviously, the tether is covered by an insulatingjacket to protect the tether loop against electrical contact with thekey. The tether retaining tubes preferably are tubular and hollowinside. In this way, the tag assembly can be reused many times withdifferent keys simply by clipping off the locking ends 28 and 29 of aused tether, allowing them to fall into the tether retaining tubes, andlocking a new tether in place.

[0030] With a key tethered to the assembly of FIG. 1, the assembly canbe inserted into a slot of a Key Track system in the usual way. However,the touch memory device of this enhanced tag assembly can onlycommunicate with the Key Track controller when the tether is connectedto the tether retaining tubes completing the electrical path between thecontact pad 26 and the hidden contact surface of the touch memorydevice. Thus, as long as the key is tethered to the assembly, itfunctions in the usual way with the Key Track system. However, if thetether is cut while the tag is inserted in a slot of the Key Tracksystem in an attempt to defeat the system and steal the key, the systemwill loose communication with the touch memory device on that tag. Whenthis occurs, the Key Track controller will note erroneously that thecurrent authorized user (the user who entered an approved code to accessthe Key Track drawer in the first place) has checked out the tag.Accordingly, when a subsequent user or management notices that the keyhas been cut off of the card, the person logged by the controller ashaving checked out the key is the obvious and isolated suspect. In somesystems, a user may only be authorized to remove certain specified keysfrom the entire set of keys in the Key Track unit. If this user accessesthe system and then clips or cuts of a key he does not have authority toaccess, the system immediately notes an improper access and can sound analarm. Not only will the perpetrator be identified, but the generalknowledge that such identifications will be made substantially detersattempts to tamper with or defeat the system.

[0031]FIG. 2 illustrates an alternate embodiment of a tamper deteringkey tag assembly. This embodiment is similar in many respects to that ofFIG. 1, but is usable with a Key Track system wherein ID codes arestored in a radio frequency identification tag (RF tag) and transmittedto the Key Track system via RF transmission. As with the embodiment ofFIG. 1, the tag assembly comprises a card 36 having a main body 37 and adepending tongue 38. A pair of tether retaining tubes 42 and 43 arefixed to the card 36 and a conducting tether 49 has locking ends 51 and52 adapted to be pressed and locked into the open ends 44 and 46 of theretaining tubes. The tether loop 53, which extends between the ends,extends through the opening 54 of a key 56 for securing the key to thetag assembly.

[0032] In this embodiment, an RF antenna comprising a pair of capacitiveplates 39 is formed on the depending tongue 38 of the card 36. Theintegrated circuit chip 41 of the RF tag is connected by a trace on theboard directly to one of the capacitive plates 39 of the capacitiveantenna and to the other capacitive plate through the circuit formed bythe tether retaining tubes and the tether. Thus, as long as the tetheris intact, the key tag assembly functions normally by transmitting thecode of the RF tag to the controller via the capacitive plate antennawhen the tag is located in a slot of a Key Track storage container.However, if the tether is cut without removing the tag from the storagedrawer, the controller looses communication with the tag and notes thatthe current user checked it out. Subsequently, as with the embodiment ofFIG. 1, the user and thief can be identified through a review of thecheck out logs of the controller.

[0033]FIGS. 3 and 4 illustrate yet another embodiment of the tamperdetering key tag assembly of this invention. In this embodiment, a keycard 61, formed of printed circuit board or other appropriate material,has a main body 62 and a depending tongue 63. The card carries an RFtag, which includes an integrated circuit chip 67 and a pair ofcapacitive plate antennas 64 and 66 disposed on the depending tongue ofthe card. Conducting traces 68 and 71 are formed on the card and definea part of an electrical circuit connecting the capacitive plates of theantenna to the integrated circuit chip. Each trace 68 and 71 terminatesat the top of the card in a corresponding one of the contact pads 72 and73. A conducting tether 76 (FIG. 4) has generally U-shaped spring biasedclip ends 77 and 78 connected by a tether loop 79, which is extendablethrough the opening 82 of a key 81. The clip ends 77 and 78 are adaptedto be clipped over respective ones of the contact pads 72 and 73 totether the key securely to the card. The clipping of the clips to thecontact pads also completes the circuit between the capacitive plates ofthe antenna and the RF tag chip 67. A protective sheath 74 can be slidover the card to cover and protect the card and the locking clips.

[0034] It will be seen that the embodiment of FIGS. 3 and 4 functions insubstantially the same way as the embodiment of FIG. 2 in an RF KeyTrack system.

[0035]FIG. 5 illustrates an alternate embodiment of the invention foruse in securing loose objects other than keys, such as, for example,jewelry, in a Key Track system and for detecting attempts to defeat ortamper with the system by cutting or destroying the bag. In thisembodiment, a bag 86 is provided for receiving and containing an objector objects to be tracked. The bag 86, which may be made of any suitablematerial such as cloth, nylon, or the like, is provided with strands 87of conducting material that are configured to form a grid or mesh thatencases the bag. In the preferred embodiment, the bag has amulti-layered structure and each tier of the grid is formed on arespective layer of the bag. The mesh can also be attached to the bag inany other suitable way such as, for example, being sewn into the liningof the bag. The conductive strands 87 in each layer of the bag thattogether form the mesh terminate in contact pads 88 and 89 at the opentop portion of their respective layers of the bag. If desired, theentire outer surface of the bag can be provided with a conductive outerlayer for further protection.

[0036] A hinged clip 91, which may be made of plastic or other suitablematerial, is provided for sealing the top of the bag and thus closing anobject in the bag. The hinged clip 91 has a fista side 92, a second side93, and one of the sides is formed with a projecting tongue 94 adaptedto be inserted into a slot of a Key Track system. The tongue is providedwith a touch memory device for transmitting an identifying code to thecontroller of the Key Track system in the traditional way when thetongue is inserted into a slot. An RF tag may alternatively be usedinstead of a touch memory device.

[0037] A first locking pin 99 projects from one of the sides of the cliptoward the other side, which is formed with a locking hole 102 alignedwith the locking pin. The locking hole is sized such that when thelocking pin is pressed through the hole, the pin is locked securely inplace within the hole. Similarly, a second locking pin 101 extends fromthe one side toward an aligned locking hole 103 formed in the otherside. One contact surface of the touch memory device 96 is electricallyconnected to locking pin 99 by a conducting trace 97. The other lockingpin is electrically connected to a contact pad 90 formed on the back ofthe projecting tongue 94. The locking pins are made of a conductingmaterial such as metal.

[0038] In use, an object to be secured and tracked is placed in the bag86. The locking clip 91 is then placed over the open end of the bag andpositioned such that when the locking clip is squeezed shut, each of itslocking pins pierce, extend through, and make electrical contact with arespective one of the contact pads 88 and 89 that terminate theconductive strand of the mesh. Thus, a closed conducting circuit isformed from one of the contact surfaces of the touch memory device,through the mesh, and to the contact pad on the back of the tongue. Thetongue can then be inserted in a slot of a Key Track system, where thecode of the touch memory device is read in the usual way.

[0039] When the bag is closed with the clip, the locking pins of theclip lock into place within their respective locking holes to seal thebag securely. Preferably, the clip can only be unlocked to retrieve thecontents of the bag by authorized personnel using a special unlockingtool. If a would be thief attempts to cut the bag and remove the objectinside with the tag intact within a Key Track receptacle, the connectionbetween the touch memory device and the system controller will be brokenbecause the mesh strand will be severed. In this event, the Key Trackcontroller will note in its log that the bag has been removed by theperson who accessed the system with his or her authorization code. Whenit is later discovered that the bag has been compromised, a review ofthe access log will reveal the thief, as with previously discussedembodiments. Alternatively, if a user with access to the system butwithout authority to access a particular bag cuts or tampers with thebag, this event is detected and alarm generated immediately.

[0040]FIGS. 6, 7, and 8 illustrate an alternate and more robustembodiment of the present invention. More specifically, the embodimentsof FIGS. 1 through 5 suffer from the requirement that a humansubsequently notice that a key or bag has been compromised and check theaccess logs to reveal the thief. In addition, the system, although moresecure than the traditional Key Track system, still may be defeated by,for example, jumpering the conductive tether before it is cut andrepairing the cut before removing the jumper. The embodiment of FIGS. 6,7, and 8 addresses this vulnerability.

[0041] Referring to FIG. 8 first, a key tag assembly 121 comprises a keycard 122, which preferably but not necessarily is formed of printedcircuit board material. The key card 122 has a main body 123 and adepending tongue 124. A capacitive plate RF antenna is defined by a pairof capacitive plates 126 and 127 formed, preferably with printed circuitboard etching techniques, on either side of the depending tongue 124. Aspaced pair of tether retaining tubes 128 ad 129 are mounted to the mainbody 123 and each has an open end formed with an internally extendinglocking rim as described above. A tether 106 has spring loaded lockingends 108 and 109 respectively connected by a tether loop 110. As withprior embodiments, the tether is adapted to be extended through theopening 132 of a key 131 and its ends snapped into the open ends of thetether retaining tubes 128 and 129 to tether and secure the key 131 tothe key card 122. A protective sheath (not shown in FIG. 8) may beprovided as in prior embodiments to encase the card and protect thecomponents thereof.

[0042] A tag circuit 133, which may include a micricontroller chip andother related electronics (FIG. 9) is mounted to the main body 123 ofthe key card 122 and is powered by an on board battery 139 connected tothe microcontroller 133 via conductive traces 137 and 138 formed on thekey card 122. The tag circuit 133 also is electrically connected to thetether retaining tubes 128 and 129, which preferably are made ofelectrically conductive material, via conductive traces 141 and 142. Apair of conductive traces 134 and 136 connect the microcontroller andtag circuit to contact plates 126 and 127 on the tongue of the key card122. The microcontroller is programmed with an ID code that can becommunicated to the main controller of a Key Track system through thecontact plates. Radio frequency transmission through an antenna may alsobe used, as described in more detail above. Alternatively, a standard RFtag could be provided on the card and controlled by the microcontrollerto transmit its code. The contacts shown in FIG. 8 as a preferredembodiment and is considered to be one best mode of carrying out theinvention.

[0043]FIG. 6 illustrates the tether 106 of this embodiment in moredetail. The tether 106 has spring loaded locking ends 108 and 109connected by a tether loop 107. The tether loop 107 is formed with aninternal strand of resistive material 111 surrounded by a dielectricinsulator 112 and an outer protective casing 113, forming a coaxialstructure. Thus, the tether, rather than being conductive as with priorembodiments, has a specific resistance determined by the resistivity ofthe resistive strand 111 and its length. When the tether is locked inplace in the tether retaining tubes, this resistance is coupled to themicrocontroller 133 as illustrated schematically in FIG. 7.

[0044] In general, the embodiment of FIGS. 6 through 8 functions toprovide tamper detection as follows. A more detailed description isprovided below. The battery 139 supplies operating power to themicrocontroller, which is programmed to generate a small current throughtraces 141 and 142 and through the attached resistive tether 106. Themicrocontroller monitors the resulting voltage drop across the resistivetether through its digital-to-analog (D/A) converters. If thisresistance changes, then it is likely that the tether has been cut,jumppered, or damaged in some way. Upon detection of a resistancechange, the microcontroller/tag circuit generates a signal indicative ofa suspected tampering and transmits this signal to the central Key Trackcontroller through the contact plates, just at the ID code istransmitted under normal conditions. The central controller can thenrespond by issuing the appropriate alarms and notifying securitypersonnel of a suspected tampering or attempt to defeat the system.Thus, detection of tampering in this embodiment is immediate and doesnot require that a human operator subsequently notice that the tetherhas been cut. Accordingly, this embodiment is more robust and reliablethan some prior embodiments, although not as economical. Further, withon-board intelligence provided by the microcontroller, a record oftampering situations or other information can be stored directly on thekey card, including the number of detected tamperings and their times.

[0045]FIG. 9 is an electronic schematic of a preferred circuit for usein the embodiment shown in FIGS. 6 through 8. The microcontroller 133 isseen to be powered by the battery 139 and is connected through I/O portsP02 and P03 to the resistive tether 106. A crystal oscillator provides aclock signal for operation of the microcontroller and the capacitiveplates 126 and 127 of the capacitive plate antenna are connected throughan N-channel MOSFET inverting switch to I/O ports PO0 and PO1. Asdescribed above, the microcontroller is programmed to generate a smallcurrent through the resistive tether 106 and to monitor the resultingvoltage drop across the tether for detecting a change in the resistanceof the loop. Upon initial attachment of the tether to the key tagassembly, the microcontroller reads the voltage drop of the new tetherand stores this value for future comparison in detecting changes in theresistance of the tether. Since each tether has a different resistanceand since these resistances are unknown to a potential thief, jumperingthe tether prior to cutting it in an attempt to defeat the system isvirtually impossible. The very act of attaching the jumper creates aparallel resistance that lowers the apparent resistance of the tether.Accordingly, an attempt to jumper the tether is itself detected andresults in an alarm. It will thus be seen that the resistive tetherembodiment provides a significantly higher level of security thansimpler conductive tether designs.

[0046]FIGS. 10 and 11 illustrate a security device usable with theenhanced key tag of this invention to address another vulnerability, thepossibility that a thief will simply cut the key itself to remove itfrom its tether without damaging the tether. It is generally easy to cutkeys in this way with a simple pair of wire cutters since keysinherently are made of soft metal to facilitate key manufacture andduplication. To prevent this eventuality, a generally U-shaped shroud148 is formed of stainless steel or other hardened material and has afirst side 149 and a second side 150. Rough inner surfaces 151 areformed on the sides of the shroud for gripping the key and alignedopenings 152 are formed through the sides for receiving a tether 153(FIG. 11). In use, the shroud 148 is slipped over the end of a key 146covering the opening 147 thereof. A tether is then inserted through theopenings in the shroud and through the key opening to attach the key toa key card as described above. The shroud thus protects the weakestparts of the key from easy access with wire cutters. The steel shroud issized so that no axial spinning of the key inside the shroud can exposethe weakest part of the key. Thus, it is difficult to cut the key offits tether and, even if the key is cut, may be unusable.

[0047] The invention has been described herein in terms of preferredembodiments. It will be understood, however, that other embodiments andtechniques are possible and usable within the general scope of theinvention. For example, the tethers have been described as beingconductive or resistive. However, other envisioned tether technologiesapplicable to the invention include compressed gas/vacuum/fluid filledtethers, elastic trigger tethers, reflective wave tethers, andpiezoresistive tethers. In a compressed gas type tether, the tether istubular and is filled with a substance (gas/vacuum/fluid, etc.) thatcauses a pressure difference with the normal atmospheric pressure. Thispressure differential is harnessed to apply a force to or release aforce from an actuator such as a switch in the tether. The actuator,when in its normal condition, indicates that the tether loop is in anormal non tampered state. If the tether is cut, damaged, or otherwisetampered with in such a way as to breach the tether, the pressure in thetether normalizes to ambient pressure, releasing the actuator toindicate a tampered condition and this is conveyed to the centralcontroller for action.

[0048] In an elastic trigger type tether, an elastic member is disposedand stretched within the tubular tether. The elastic member is attachedat one end to an end of the tether and its other end is attached to asensor such as a switch or optical interrupter. If the tether is cut torelease the protected object (key, etc.) the elastic member relaxes andreleases the sensor, indicating a tampered condition.

[0049] In a reflective wave type tether, the tether is configured tofunction as a waveguide (such as a coax line or an internal fiber opticcable). A wave is launched into the one end of the waveguide, which isterminated at its other end with a matching line impedance, and amonitoring system on the key tag samples for any reflected waves. Aslong as the tether is intact, the matched line impedance at the otherend of the waveguide insures that no or only expected reflections willbe generated. If the tether is cut, altered, damaged, or shorted,unexpected reflected waves in the guide are generated and suchreflective waves are detected and signaled to the central controller toindicate a possible tampering condition.

[0050] A piezoresistive tether contains a piezoresistive element whoseresistance changes with length or cross-sectional area. This phenomenacan be utilized in a tether to sense compression and tension forces onthe tether that may be early indicators of tampering. If the tether iscut, this is detected through the complete loss of continuity throughthe tether.

[0051] In addition to electronic detection of tampering or attemptedremoval on an object, simpler user level approaches are also envisioned.These approaches include, for example, filling a hollow tether with ahighly identifiable and bright colored marking dye to mark a stolen keyor other object and the person who took it if the tether is cut toremove the object. Other possibilities include filling the tether with apungent odor producing material or with a material that would produce asound when released to draw attention to a would be thief.

[0052] These and other additions, deletions, and modifications mightwell be made to the disclosed embodiments without departing from thespirit and scope of the invention as set forth in the claims.

What is claimed is:
 1. An enhance key tag assembly for use with a KeyTrack system comprising a key card, an ID code stored on said key card,means for communicating the ID code to a central controller of a KeyTrack system, a tether connecting a key to the key card, and means fordetecting tampering with the tether as an indication of an attempt toremove the key from its card.
 2. The key tag assembly of claim 1 andwherein said means for detecting tampering comprises a conductive tetherand wherein the ID code is communicated to the central controllerthrough said conductive tether, the communications link being broken ifsaid tether is cut.
 3. The key tag assembly of claim 1 and wherein saidmeans for detecting tampering comprises a resistive tether and means onsaid key tag for monitoring a voltage drop across said resistive tether,a change in voltage drop indicating that the tether has been cut ortampered with, and means for communicating the detected voltage drop tothe central controller of a Key Track system.
 4. The key tag assembly ofclaim I and further including a shroud covering at least a portion of akey attached to the tether to protect the key from being cut and removedfrom said tether.
 5. The key tag assembly of claim 1 and furthercomprising tether retaining means on said key card, said tetherretaining means lockably receiving ends of said tether to attach saidtether to said key card.
 6. The key tag assembly of claim 1 an whereinsaid means for communicating comprises a touch memory device attached tosaid card.
 7. The key tag assembly of claim 1 and wherein said means forcommunicating comprises an RF antenna on said card.
 8. The key tagassembly of claim 7 and wherein said RF antenna comprises a capacitiveplate antenna.
 9. The key tag assembly of claim 7 and wherein said RFantenna comprises an inductive loop antenna.
 10. A method of detectingtampering with a tether securing an object to an identification tag,said method comprising the steps of: (a) monitoring a preselectedcharacteristic of the tether; and (b) noting a tampered-with conditionif the preselected characteristic of the tether changes.
 11. The methodof claim 10 and wherein the preselected condition is the electricalconductivity of the tether and wherein step (a) includes passing asignal to be transmitted to the Key Track system through the tether, thesignal being interrupted to indicate a tampering condition when of thetether is cut.
 12. The method of claim 10 and wherein the preselectedcondition is the resistance of the tether and wherein step (a) includesmonitoring a voltage drop across the tether, a change in the voltagedrop indicating a tampering condition.
 13. A protective shroud forinhibiting tampering with a key comprising a shroud body configured tobe received over and cover at least portion of the key to protect saidportion from being cut.